In the last ten years there has been a tendency to use gravimetric techniques or weighing, for filling liquid in containers, rather than the conventional volumetric filling.
Many filling machines consist mainly of a rotating table which has a plurality of weighing devices and filling heads. These weighing devices and filling heads are installed on the rotating table, whereby the weighing is performed during rotation and the weighing devices are subject to rotational acceleration.
One of the most common weighing devices for the filing machine application is a load cell which is a transducer for forces or weights. The load cell is normally installed on a line radiating from the center of the rotating table. The load cell has a lower mounting area at one end, which is fixed to the rotating table, and a load mounting area at the other end. When subject to a load, the load mounting area has a downward deflection. The rotational acceleration, which when multiplied by mass creates centrifugal force, is acting on the deflected mass to create a force moment which interferes with the accuracy of the weighing.
The following ten (10) prior art patents were uncovered in the pertinent field of the present invention:
1. U.S. Pat. No. 2,603,442 issued to Snyder et al. on Jul. 15, 1952 for "Apparatus For Weighing And Bagging Materials" (hereafter "the Snyder Patent"); PA1 2. U.S. Pat. No. 2,901,209 issued to Bardy et al. on Aug. 25, 1959 for "Container Filling Machine" (hereafter "the Bardy Patent"); PA1 3. U.S. Pat. No. 3,215,173 issued to Rutherford on Nov. 2, 1965 for "Bag Filling And Weighing Machine" (hereafter "the Rutherford Patent"); PA1 4. U.S. Pat. No. 3,339,651 issued to, Garnett on Sep. 5, 1967 for `Weighing Apparatus" (hereafter "the Garnett Patent"); PA1 5. U.S. Pat. No. 4,037,675 issued to Storace et al on Jul. 26, 1977 for "Leaf Spring Weighing Scale" (hereafter "the Storace Patent"); PA1 6. U.S. Pat. No. 4,230,195 issued to Graffin on Oct. 28, 1980 for "Automatic Control Method And Device For A Container Filling Apparatus" (hereafter "the Graffin Patent"); PA1 7. U.S. Pat. No. 4,582,102 issued to Risser on Apr. 15, 1986 for a means For Electronically Comparing The Extent Of Fill In Containers With A Preset Extent" (hereafter "the Risser Patent"); PA1 8. U.S. Pat. No. 4,632,198 issued to Uchimura on Dec. 30, 1986 for "Multi-Range Load Cell Weighing Instrument" (hereafter "the '198 Uchimura Patent"); PA1 9. U.S. Pat. No. 4,690,230 issued to Uchimura et al on Sep. 1, 1987 for "Multi-Range Load Cell Weighing Instrument" (hereafter "the '230 Uchimura Patent"); and PA1 10. U.S. Pat. No. 4,928,473 issued to Nagao et al on May 29, 1990 for "Device For Automatically Filling And Packing Predetermined Weight Of Product In Containers" (hereafter "the Nagao Patent").
The Snyder Patent discloses an apparatus for weighing and bagging materials. It includes a rotary weighing machine which has weighing units and are moved around a table.
The Bardy Patent discloses a container filling machine. The filling machine has a plurality of interrelated operations to dispense accurately measured and accurately weighed quantities of a material.
The Rutherford Patent discloses a bag filling and weighing machine. It includes a rotatable hub assembly with a circular platform. A plurality of scale supporting frame members are arranged to extend radially from the platform. A fixed bag supporting means is carried by each scale so that the weight in. an attached bag will activate on the scale.
The Garnett Patent discloses a weighing apparatus. It includes a continuously traveling weigher head and a material receptacle. The weigher head has a scale beam supporting the receptacle. There is means to operate the receptacle during a phase in the cycle of the head travel to trim off therefrom an overweight of material.
The Storace Patent discloses a leaf spring weighing scale. The scale includes a weighing pan for receiving a load, and which is movably responsive to the load. A movable load support structure supports the weighing pan. A pair of load cells support the load support and measure its deflection. The load cells are arranged in tandem with one load cell being operative through a given portion of the weight range and the other being operative through the remaining portion of the weight range.
The Graffin Patent discloses an automatic control method and device for a container filling apparatus. The method includes the steps of sequentially taking containers filled in a multi-station filling machine. The weighing device at the weighing station of the transfer apparatus generates signals which are an image of the sensed weight of the successive containers sensed by the weighing device.
The Risser Patent discloses a means for electronically comparing the extent of fill in containers with a preset extent. It includes a rotary filling machine which has a rotating platform with stations on which bottles are supported for filling with liquid dispensed through filling head assemblies at each individual station.
The '198 Uchimura Patent discloses a multi-range load cell weighing instrument. It includes a high weighing load cell positioned adjacent a base and a low weighing load cell positioned adjacent a tray. The load cells are located such that the center lines along the length substantially coincide with the center line of the tray.
The '230 Uchimura Patent discloses a multi-range load cell weighing instrument. It includes means for supporting an article to be weighed, a low range load cell and a high range load cell. The low range load cell has a high accuracy weighing range and has means for outputting a first signal in response to a weight on the supporting means. The high range load cell has a high load weighing range which is higher than the high accuracy weighing range. The high range load cell includes means for outputting a weight signal as a function of one of the first and second signals.
The Nagao Patent discloses a device for automatically filling and packing a predetermined weight of product in containers. It includes a rotary table which has a plurality of weighing heads radially arranged and each provided with a weigher which includes a packing container holding mechanism instead of the weigh hopper.
None of these prior art patents have disclosed a weighing device which is designed and constructed for compensating dynamic forces in rotary machines, so that the weight of an object can be weighed accurately during rotation of the rotary table of the rotary machine. It is desirable to have a very efficient and also very effective design and construction of a weighing device which utilizes at least two load cells which are integrally connected to each other to thereby form a unitary device which has the load cells oriented to provide dynamic force compensation.